Dustin: I heard my grandma say once that most diabetics have bad circulation of their blood. Is that true?
Dr. Ponds: That is quite true, Dustin. Circulatory problems are a major complication of diabetes.
Dustin: What causes bad circulation for diabetics?
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GLOSSARY Atherosclerosis- A condition common to diabetics where plaque builds up within the walls of arteries and in time may completely prevent blood flow. Arteries- Thick-walled blood vessels that carry blood from the heart toward cells in the body. |
Dr. Ponds: A disease called atherosclerosis produces most of the circulatory problems observed in diabetics. Atherosclerosis, literally translated from Latin, means hardening of the arteries. Arteries are thick-walled blood vessels that carry oxygen- and nutrient-rich blood away from the heart toward peripheral tissues and cells in the body. Without the oxygen and nutrients supplied by arteries, cells and tissues die.
Dustin: Arteries are pretty important then?
Dr. Ponds: Healthy arteries are very important for having a healthy body.
Dustin: What do arteries look like close up?
Dr. Ponds: Here, Dustin, let's take a look at this diagram of normal blood vessels. The red vessel to the left is an artery, which we want to know about.
In healthy arteries, the lumen is the open space through which blood flows. Three tissue layers called tunicae, or coats, surround the lumen. The tunica intima, or internal coat, is the innermost layer, composed of endothelial cells and a thin layer of protein called the internal basement membrane. Smooth muscle cells comprise the tunica media, or middle coat. The muscle cells contract or relax to constrict or dilate the artery. The tunica adventitia, also called the outer coat, is composed of connective tissue containing elastic fibers and another layer of protein called the external basement membrane.
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GLOSSARY Lumen- The interior space of an artery through which blood flows. Tunicae- (plural) Latin for "coats." Tunica intima- The "inner coat" or inner layer of the wall of an artery. Endothelial cells- Connective tissue cells. Internal basement membrane- A thin layer of protein within the tunica intima of an artery. |
Dustin: Is hardening of the arteries, I mean, is atherosclerosis when the muscle cells get overworked and stiffen up?
Dr. Ponds: Excellent guess, Dustin, but that is not quite correct. Atherosclerosis is the emergence of a plaque between the basement membrane and the endothelial cells of the tunica intima.
Dustin: What's a plaque?
Dr. Ponds: A plaque consists of lipid, or cholesterol fused with proteins, and a fibrous cap of connective tissues. Eventually, the plaque solidifies, becoming a stiff layer of material within the tunica intima.
Dustin: Is the plaque there for good?
Dr. Ponds: Plaque within an artery is permanent. It's not coming out.
Dustin: OK, so a hard, unmovable plaque forms in the artery. Then what happens?
Dr. Ponds: Over time, further cholesterol and lipoprotein exposure enlarges the plaque. While the plaque grows, it pushes the tunica intima inward, literally forcing the vessel wall to expand. The growing arterial wall engulfs more and more of the space of the lumen and limits blood flow. I'll show you what I mean. Look at these pictures I have of arteries. On the left is a cross-section of a healthy artery with a large, unobstructed lumen. The artery on the right suffers from atherosclerosis.
Dustin: Man, the one on the right is completely closed. Is all of that stuff plaque?
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GLOSSARY Tunica media- The "middle coat" or middle layer of the wall of an artery. Tunica adventitia- The "outer coat" or outer layer of the wall of an artery. External basement membrane- A thin layer of protein within the tunica adventitia of an artery. |
Dr. Ponds: The artery on the right is certainly blocked, but not all the blockage stems from plaque. You can see the plaque in the upper right part of the vessel. The plaque has caused the wall to bulge inward.
Dustin: What is that large blockage in the middle of the artery?
Dr. Ponds: That takes some explaining. As the plaque builds up, the blood deprivation level of the destination tissue increases. The body attempts to get more blood through the narrowed vessels to the malnourished tissue, increasing blood pressure. The elevated blood pressure creates a higher cholesterol and lipoprotein concentration, which continues a vicious cycle of plaque enlargement and blood pressure elevation.
Dustin: I don't know what you mean.
Dr. Ponds: Basically, the plaque is like a traffic accident during rush hour. The accident blocks up the highway, which slows down traffic, but causes driver impatience and frustration levels to soar, which causes more accidents.
Dustin: Oh, I got it now!
Dr. Ponds: Excellent! Now then, the plaque grows and grows, but before total closure of the artery occurs, the hardened plaque may also rupture the lining of the vessel, creating a blood clot, or thrombus. A thrombus may then break away and plug the artery further downstream as the arterial diameter decreases.
Dustin: So, it's a thrombus that I see in the very center of the artery.
Dr. Ponds: That is exactly correct. Once the artery is clogged, usually by a thrombus, the tissue on the receiving end of the vessel dies. In the heart, arterial blockage causes a heart attack. An occluded artery in the brain causes a stroke. Large vessels that develop plaques may have weak walls that can rupture, causing an aneurysm. Loss of blood supply to an extremity, especially the foot in diabetics, leads to poor healing, infections, then gangrene.
Dustin: Who is at risk for getting atherosclerosis?
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GLOSSARY Plaque- A hardened deposition of lipid within an artery covered by fibrous tissue. Lipid- A fat molecule. Cholesterol- (see lipid). Lipoprotein- A lipid combined with a protein molecule. Thrombus- A blood clot within an artery. |
Dr. Ponds: Older males who have a family history of circulatory problems are at high risk for atherosclerosis. Cigarette smoking, limited exercise, obesity, and a diet high in carbohydrate or high in cholesterol and saturated fat are manageable high-risk factors for atherosclerosis. Diabetes can be a minimal problem if patients manage their blood-glucose level properly, as your grandmother has proven.
Grandma: I never let my blood-glucose take control of me. I take control of it.
Dustin: I'm glad that you do, Grandma. What causes atherosclerosis, Dr. Ponds?
Dr. Ponds: Some people are genetically susceptible to formation of plaques, while others are not genetically susceptible. Those that are susceptible form fatty streaks in the tunica intima at a young age. A fatty streak emerges when the endothelial cells are subjected to large concentrations of cholesterol and lipoproteins in the blood. Prolonged exposure to cholesterol and lipoproteins transforms the fatty streaks into a plaque.
Dustin: Does Type II diabetes cause atherosclerosis?
Dr. Ponds: Yes, but atherosclerosis is not caused exclusively by diabetes. A combination of genetic susceptibility and high-risk diet initially causes atherosclerosis. Diabetes compounds the effects of the genetic and dietary intake factors on blood vessels.
Dustin: I think I understand atherosclerosis. What other complications are there?
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